EP0901418B1 - Vehicle with controlled-level suspension - Google Patents

Description

The invention relates to a vehicle with a level-controlled suspension system, especially a vehicle with level control Air suspension, with the level control independent of one Operate a service brake of the vehicle to work and a suspension system for level control assigned, on the input side with sensors for level detection connected control circuit is connected to signal transmitters, which is an actuation of a main service brake of the vehicle to capture.

Such a vehicle is the subject of DE 38 15 859 C2.

Air suspensions for motor vehicles are generally known and are used as standard. As a rule it is on the pressure side a pneumatic pressure accumulator is provided for a compressor, which is kept at a boost pressure by the compressor which is significantly above the operating pressures of the respective air suspension units or bellows.

Attempts have also been made to use the pressure accumulator for air suspensions to spare and the air suspension units or bellows if necessary, feed directly from the compressor with compressed air. This is especially possible if the air filling the air suspension units essentially only with a lowering or raising the level of the vehicle, but not at normal spring strokes is changed.

In vehicles with such air suspension systems is regular provided the ventilation of the air suspension units depending on the level.

For the rest, level control is also available for other suspension systems basically known. For example parallel to passive suspension elements, e.g. Coil springs, additional controllable support members can be arranged, that work, for example, hydropneumatically.

If a level control responds when the vehicle is with operated service brake, which on all vehicle wheels acts, is held in the state, can cause considerable chassis tension occur, with the result that the vehicle a sudden lifting or lowering movement when releasing the brake executes. To avoid this, the DE 38 15 859 C2 proposed that the control system of level regulation responsive to a lock indicator signal, which is generated when vehicle wheels are applied by the service brake of the vehicle are kept immobile. In one In such cases, the level regulation enables Height adjustment limited to values within a range, that of the brake application and stationary vehicle remaining movement play of the wheels is dependent. To put it simply, the measure of a possible height adjustment is expressed with the vehicle stationary and the service brake applied compared to the extent of the possible height adjustment clearly limited when the vehicle is moving.

From DE 37 13 640 A1 a vehicle is known in which hydraulic lines both for the service brake system as well a level control of the vehicle can be used. A priority circuit ensures that the lines are only available for the braking system, when the driver presses the brake pedal or the like. operated. A level regulation Accordingly, it can only be used when the service brake is not applied respectively. The system of DE 37 13 640 A1 offers thus possibility of manufacturing costs through double use saving of hydraulic lines, however, is a compensation brake nodding movements and the like. of the vehicle possible.

The object of the invention is now, the respective use of the vehicle even more adaptable level control create.

This object is achieved in that further Signal generator falls below a low threshold the driving speed and the control circuit the level control for a given or predefinable Delay time - e.g. 30 seconds - interrupts or Condition of the suspension system remains unchanged when a Brake actuation signal and a signal for falling below the Threshold values are present.

The invention is based on the general idea that each Vehicle level largely unchanged for a shorter time to be left when the vehicle is operated Main service brake is stopped or when the Main service brake only at extremely low speed moves. It is taken into account here that the typically Main service brake acting on all vehicle wheels when the vehicle is stationary or almost stationary of the vehicle wheels compared to the vehicle body reduced because such lifting movements in modern Undercarriages are connected with further wheel movements that are made more difficult by the main service brake applied. In particular, the wheelbase can change during suspension strokes, i.e. the vehicle wheels lead relative to each other Suspension strokes movements in the vehicle's longitudinal direction. Such Movements are in the state of the vehicle when actuated Main service brake only possible with difficulty. In addition comes that the braking torque of the vehicle wheels regularly Actuate wheel control arm, which with suspension strokes Carry out swiveling movements around a vehicle transverse axis. Should a wheel control arm adjusted one compared to its normal position Take up position when the vehicle stops and with actuated Main service brake is held in position, so can the adjusted wheel control handlebars are not easily in swivel their normal position back. Rather, the chassis or the suspension system through the main service brake in one kept tense state.

When the main service brake is released, the suspension can again go back to their normal state, so that one at Braking occurred and due to the vehicle at a standstill Main service brake applied maintains level change can compensate automatically without it a level-regulating intervention in the suspension system requirement.

Since according to the invention with the vehicle stationary and actuated Main service brake usually no level regulating Interventions are carried out, these interventions can not be undesirable Level settings lead if the Main service brake is released again or the vehicle starts. Accordingly, level corrections that would otherwise be necessary superfluous when starting the vehicle.

According to a particularly preferred embodiment of the invention can the control circuit on the input side with a signal transmitter, which detects an opening of a vehicle door, connected be a level control regardless of the operating state to allow the main service brake when at a standstill a vehicle door is opened.

In this way it can be taken into account that the loading state of a vehicle typically with the vehicle open Vehicle door changed and a regulation accordingly of load-dependent level changes is desirable.

To automatically perform level corrections with high Probably limit to what is necessary can, can also be provided when standing Vehicle and main service brake applied in any case only carry out limited level corrections. With that, in in any case take into account that when the service brake is applied and stationary vehicle always a level change to one Changes in the tension of the chassis leads and the Release the service brake and the associated dismantling of the Tensioning spring strokes are not sufficiently precise are assessable.

Otherwise, with regard to preferred features of the invention to the claims and the following explanation of Drawing referenced, based on the particularly preferred variants of the invention are described.

Fig. 1

eine schematisierte Seitenansicht eines Kraftfahrzeuges, dessen Hinterachse eine niveaugeregelte Luftfederung aufweist, in Normallage,

Fig. 2

eine der Fig. 1 entsprechende Seitenansicht des Fahrzeuges in (übertrieben dargestellter) starker Nickstellung und

Fig. 3

eine schaltplanartige Darstellung eines zur Niveauregelung einer Luftfederung dienenden erfindungsgemäßen Systems.

It shows

Fig. 1

2 shows a schematic side view of a motor vehicle, the rear axle of which has a level-controlled air suspension, in a normal position,

Fig. 2

1 corresponding side view of the vehicle in (exaggerated) strong pitch position and

Fig. 3

a circuit diagram-like representation of a system for level control of an air suspension system according to the invention.

Has a motor vehicle 1 designed as a people carrier its front wheels 2 assigned struts 3 more conventional Kind with helical compression springs. With suspension strokes the front wheels 2 of the struts 3 in cooperation with wheel guide members, not shown, such as Trailing and wishbones, relative to the vehicle body on one Route V shown in dashed lines, which in example shown slightly oblique to the vehicle vertical axis runs.

Even if the respective load in such MPVs can be very different, this affects the Shock struts 3 only slightly, i.e. the ground clearance of the Motor vehicle 1 remains independent in the area of the front wheels 2 largely the same from the respective payload.

The rear wheels 4 are associated with air bellows 5, which in enable level control shown below, so that a desired ground clearance of the vehicle body regardless of the respective payload, its change too lead to significant changes in load of the air bellows 5 can, is adjustable.

The rear wheels 4 are inter alia by inclined or Trailing arm 6 guided, the suspension side to their body side Bearing pivot and the rear wheels 4 relative to Run assembly on arched tracks H.

The vehicle 1 has a service brake in the usual way, on both the front wheels 2 and the rear wheels 4 works. This service brake is only one of them Actuating pedal 7 indicated. The braking torque of the Wheel brakes are applied to the front wheels 2 in the usual way via the struts 3 and on the rear wheels 4 via the Trailing arm 6 worn on the vehicle body.

If the vehicle 1 is braked while driving, then act on the vehicle body pitching moments, i.e. the vehicle body seeks a swiveling movement relative to the roadway around a vehicle guerilla to execute. When driving forward, this leads to that the vehicle bow relative to the lane opposite his Normal position slightly lowered and the rear of the vehicle slightly raised becomes, as shown in Fig. 2 (exaggerated).

Now the vehicle 1 also likes the position shown in FIG. 2 have at standstill, beyond like the service brake with greater force and accordingly large braking effect remain applied. This has the consequence that the pitch position of the vehicle 1 shown in FIG. 2 is not can be easily dismantled. This is especially true for the elevated position of the rear of the vehicle. Because of the actuated Service brakes are the rear wheels 4 relative to the Trailing arms 6 held practically rotationally fixed, with the result that the trailing arm 6 from its position shown in Fig. 2 only by rotating the rear wheels 4 relative to the ground in the position of Fig. 1 can pivot back. The rotation mentioned however, the rear wheels seek the motor vehicle 1 in the forward direction to move. Such a movement of the motor vehicle 1 is hampered by the braked front wheels 2.

Similar conditions exist when the rear of the vehicle stationary vehicle have an excessively lowered position and the service brake should be applied. In this case seek the relative due to the service brake applied the trailing arms 6 essentially non-rotatable rear wheels 4th to move the vehicle in reverse when the vehicle raised by strong air supply to the air bellows 5 is and the trailing arm 6 in Fig. 1 with the of the brake relative to the trailing arms 6 held almost non-rotatably Swivel the rear wheels 4 clockwise.

If the service brake is released, suspension strokes of the front wheels can take place 2 and the rear wheels 4 are again free of force, so that the ground clearance of the vehicle 1 only from its load and the respective spring forces on the struts 3 or depends on the air bellows 5. So far the vehicle 1 a desired level before applying the brake has shown and before releasing the service brake none Ventilation of the air bellows 5 has taken place, will release the previous one after releasing the service brake Restore normal level, provided that the Loading condition of the vehicle has not changed in the meantime Has.

If, on the other hand, through strong ventilation of the air bellows 5 with the vehicle stationary and the service brake applied an initial deviation from a target level would be equalized, the subsequent loosening the service brake is initially a deviating from the target level Set level so that level-regulating measures again must be carried out.

In the case of the invention explained below with reference to FIG. 3 Level control are those described above Effects taken into account to take unnecessary level-controlling measures as well as to avoid the associated energy consumption.

3, the air bellows 5 of the rear wheels 4th via shut-off valves 8 and 9 for ventilation with the pressure side a compressor 10 or for venting with the atmosphere get connected. The compressor 10 is powered by an electric motor 11 driven, which for its control (in particular Switching on and off) with the output side of a computer-aided Control circuit 12 is connected. Is on the input side the control circuit 12 connected to stroke sensors 13 whose Signals correlated with the ground clearance of vehicle construction are. In the example shown, the stroke sensors 13 cooperate the trailing arms 6 together and detect their pivot position relative to a the vehicle longitudinal axis and vehicle transverse axis containing level. Detect the stroke sensors 13 for example, the rotational stroke of the trailing arm 6 relative to Vehicle body.

Furthermore, the control circuit 12 is on the input side with a Sensor 14 coupled, the signals reflect whether the Service brake of the vehicle or that for actuating the service brake serving pedal 7 are operated or not. There in motor vehicles by actuating the service brake the brake lights must be displayed, the Sensor 14 by a brake light switch already present in the vehicle formed and a corresponding input of the control circuit 12 parallel to the brake light with the brake light switch be electrically connected. So that the brake light electrical voltage (or if not actuated brake, the then missing electrical voltage) can be used as a signal for brake actuation.

Another input of the control circuit 12 is with sensors 15 connected, which register whether one of the vehicle doors or a tailgate is open or not. Usually are the vehicle doors or the hatchback in today's vehicles combined with door switches, which with the door open or tailgate switch on the interior lighting of the vehicle. This door switch can, if necessary, in the same way how the brake light switch can be used as a sensor.

Finally, the control circuit 12 is on the input side with a Tachometer 16 or another measuring device connected, whose signals indicate whether the driving speed of the vehicle above or below a very low value which is a complete standstill of the vehicle comes close.

erkennt" also die Regelschaltung 12, ob das Fahrzeug fährt oder (nahezu bzw. bewegungslos) steht. Solange ein Fahrzustand erkannt wird, werden die Ventile 8 und 9 sowie der Elektromotor 11 des Kompressors 10 in einer für Fahrbetrieb vorgesehenen Weise betätigt, wobei nach Einstellung eines Sollniveaus im wesentlichen nur eventuelle Leckagen an den Luftfederbälgen 5 bzw. an den Ventilen 8 und 9 ausgeglichen zu werden brauchen. Darüber hinaus können gegebenenfalls auch dynamische Störkräfte, die auf das Fahrzeug 1 einwirken, ausgeregelt werden.Using the tachometer 16

Thus, the control circuit 12 recognizes whether the vehicle is moving or is (almost or motionless). As long as a driving state is recognized, the valves 8 and 9 and the electric motor 11 of the compressor 10 are actuated in a manner intended for driving operation, after adjustment of a target level, it is only necessary to compensate for any leaks in the air bellows 5 or in the valves 8 and 9. In addition, dynamic interference forces which act on the vehicle 1 can also be compensated for, if necessary.

Once the control circuit 12 based on the signals from the sensor 14 and the tachometer 16 determines that the vehicle 1 at the service brake is at a standstill, or almost the state has reached a standstill, the shut-off valves remain 8 for a predefinable delay time of, for example Closed for 30 seconds. The electric motor also remains 11 and thus the compressor 10 during this delay time switched off. This is tantamount to that initially no level-regulating measures are carried out.

If a vehicle door is opened during the delay time and a door opening signal is generated accordingly by one of the sensors 15, this is the case for the control circuit 12 Note "that it is very likely that the payload will change, for example due to passengers getting on or off a taxi "The control circuit 12 may now, regardless of whether the delay time has expired or not, initiate level-regulating measures, ie open the valves 8 and 9 for venting one of the bellows 5 or both bellows 5 or for ventilating the bellows 5 or one for the bellows 5 close the valve 9 and switch on the electric motor 11 with at least one open valve 8.

However, such level-regulating measures are carried out completely or almost stationary vehicle 1 and actuated Service brake only if there is a larger deviation from the actual value the vehicle level.

In addition, it can be provided that in this operating state the vehicle only a limited level correction is possible, such that the bellows 5 only for a limited period of e.g. 12 seconds loading or can be vented. Further level corrections are made only when driving or when operating a separate one Command (not shown) by the driver.

The same is independent of the opening or closing state of the vehicle doors provided when complete or near stationary vehicle and the service brake applied Delay time has expired. In this case too Level corrections only to a limited extent and / or only with Larger target-actual value deviations of the vehicle level occur.

As soon as the service brake is released, there is a setpoint / actual value deviation the vehicle level regardless of the Driving speed regulated, at least if that Vehicle not stopped while using an immobilizer becomes.

Claims (6)

1. A vehicle with a level-adjusted suspension system, in particular having level-adjusted air spring suspension, whereby the level control system is able to operate independently of operation of a service brake of the vehicle, and a control circuit (12) assigned to the suspension system for the purpose of level adjustment and connected to sensors (13) on the input side for detecting level is connected to signal emitters (14) which detect operation of a main service brake of the vehicle,
   characterised in that
   other signal emitters (16) detect when the travel speed falls below a low threshold value and the control circuit (12) interrupts the level control for a predetermined or predeterminable delay time - e.g. 30 seconds - leaving the state of the suspension system unchanged if a brake operation signal and a signal indicating a fall below the low threshold value of the travel speed are present.
2. A vehicle as claimed in claim 1,
   characterised in that
   the control circuit (12) is connected on the input side to a signal emitter (15) which detects when a vehicle door is opened and applies a level adjustment even if the travel speed falls below the threshold and the service brake is operated if a signal indicating an opened door is present.
3. A vehicle as claimed in one of claims 1 or 2,
   characterised in that
   when the service brake is operated and the travel speed falls below the threshold value, only a limited degree of correction can be applied.
4. A vehicle as claimed in claim 3,
   characterised in that
   air spring units (5) are pressurised or depressurised for a limit period only to apply a level correction.
5. A vehicle as claimed in one of claims 1 and 2,
   characterised in that
   the control circuit (12) is connected on the input side to a signal emitter (15) which detects when a vehicle door is opened and keeps the air spring units (5) closed during the delay time - if no signal is present indicating that a door has been opened.
6. A vehicle as claimed in one of claims 1 to 5,
   characterised in that
   if the vehicle travel speed falls below the threshold value and the service brake is operated, an active level correction is applied only if there is greater deviance in the desired-actual value of the level.

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